Very most almost likely it's mediawiki.org

• The parser tests are failing (lstParserTests). Can we get jenkins set-up to test them?

• The bug is caused by a typo in https://gerrit.wikimedia.org/r/#/c/35295/ - which I noted in https://gerrit.wikimedia.org/r/#/c/35295/5/LabeledSectionTransclusion.php but which I forgot to -1

• Patch at https://gerrit.wikimedia.org/r/#/c/37969/

I believe this typo is currently breaking all pages using LST. Because LST can't find the end marker of a labeled section, it transcludes the whole page.

[ Raising importance. Bug assigned to code submitter. ]

Adjusting importance and severity. We can't deploy 1.21wmf6 to other sites (particularly the Wikisource sites, where it's supposed to go live tomorrow: https://www.mediawiki.org/wiki/MediaWiki_1.21/Roadmap#Schedule_for_the_deployments ) until this is fixed.

Merged by Reedy.

Seems like this has been backported, so can this be closed as FIXED?

Yes, I confirm that the issue has been fixed. Thank you all.